Process Synthesis and Global Optimization of Biomass to Liquid Transportation Fuels (BTL) Systems

The transportation sector relies heavily on petroleum as a primary energy source, and currently faces challenges over high crude oil prices, volatility of the global oil market, and high levels of greenhouse gas (GHG) emissions [1].  As a result, a substantial effort has been taken in the United States to focus on greater energy independence through the utilization of more domestic energy sources.  A recent review highlights the single and hybrid feedstock design alternatives that can produce gasoline, diesel, and kerosene from coal, biomass, or natural gas [2].  Of particular interest are liquid fuels that can be derived from biomass, since the feedstock has the potential to be both a renewable energy source and a large contributor to a reduction in the well-to-wheel GHG emissions of the transportation sector.  Though corn-based ethanol and soybean-based diesel comprise a majority of the biofuels manufactured today, their use for fuel production has led to concerns regarding the impact on the price and availability of these feedstocks as sources of food [3].  Lignocellulosic plant sources including dedicated energy crops, agricultural crop residues, and forest residues are capable of being sustainable harvested without affecting the food chain and therefore expected to be a more considerable source of biofuels in the future.  The development of processes that can economically utilize these feedstocks to produce synthetic liquid fuels will be of significant importance.

We present an optimization based framework to perform a comprehensive technoeconomic, environmental, and societal assessment of an alternative energy refinery that will convert biomass to the liquid transportation fuels (BTL) gasoline, diesel, and kerosene.  Rigorous process design, global optimization, and process synthesis strategies will be utilized [4-11] to determine the optimal plant topology of a BTL refinery that minimizes the overall cost of liquid fuels production.  The cost of utility generation and wastewater treatment is treated using a simultaneous heat, power, and water integration within the process synthesis model.  Multiple case studies are presented to investigate the effect of biomass type, biomass moisture content, plant capacity, and product distribution on the optimal process topology, total plant cost, and break-even oil price.  Major topological decisions from the optimization model and the result on plant capital cost, total operational cost, and the process utility network will be discussed.

[1] National Academy of Sciences, National Academy of Engineering, and National Research Council. Liquid Transportation Fuels from Coal and Biomass: Technological Status, Costs, and Environmental Issues. Washington, D. C., EPA, 2009.

[2] C.A. Floudas, J.A. Elia, R.C Baliban.  Hybrid and Single Feedstock Energy Processes for Liquid Transportation Fuels: A Critical Review.  Comp. Chem. Eng., 2012: 41(11), 24-51.

[3] L.R. Lynd, E. Larson, N. Greene, M. Laser, J. Sheehan, B.E. Dale, S. McLangulin, M. Wang.  The role of biomass in America’s energy future: framing the analysis.  Biofuels, Bioprod. Biorefin., 2009:3(2), 113.

[4] R.C. Baliban, J.A. Elia, C.A. Floudas.  Toward Novel Hybrid Biomass, Coal, and Natural Gas Processes for Satisfying Current Transportation Fuel Demands, 1: Process Alternatives, Gasification Modeling, Process Simulation, and Economic Analysis.  Ind. Eng. Chem. Res., 2010:49(16), 7343-7370.

[5] J.A. Elia, R.C. Baliban, C.A. Floudas.  Toward Novel Hybrid Biomass, Coal, and Natural Gas Processes for Satisfying Current Transportation Fuel Demands, 2: Simultaneous Heat and Power Integration.  Ind. Eng. Chem. Res., 2010:49(16), 7371-7388.

[6] R.C. Baliban, J.A. Elia, C.A. Floudas.  Optimization Framework for the Simultaneous Process Synthesis, Heat and Power Integration of a Thermochemical Hybrid Biomass, Coal, and Natural Gas Facility.  Comp. Chem. Eng., 2011:35(9), 1647-1690.

[7] J. A. Elia, R.C. Baliban, X. Xiao, C.A. Floudas.  Optimal Energy Supply Network Determination and Life Cycle Analysis for Hybrid Coal, Biomass, and Natural Gas to Liquid (CBGTL) Plants Using Carbon-based Hydrogen Production.  Comp. Chem. Eng., 2011:35(8), 1399-1430.

[8] R.C. Baliban, J.A. Elia, C.A. Floudas.  Simultaneous Process Synthesis, Heat, Power, and Water Integration of Thermochemical Hybrid Biomass, Coal, and Natural Gas Facilities.  Comp. Chem. Eng., 2012:37(10), 297.

[9] R.C. Baliban, J.A. Elia, R. Misener, C.A. Floudas.  Global Optimization of a Thermochemical Based Hybrial Coal, Biomass, and Natural Gas to Liquids Facility.  Comp. Chem. Eng., 2012, http://dx.doi.org/10.1016/j.compchemeng.2012.03.008.

[10] R.C. Baliban, J.A. Elia, V.W. Weekman, C.A. Floudas.  Process synthesis of hybrid coal, biomass, and natural gas to liquids via Fischer-Tropsch synthesis, ZSM-5 catalytic conversion, methanol synthesis, methanol-to-gasoline, and methanol-to-olefins/distillate technologies.  Comp. Chem. Eng., submitted.

[11] J.A. Eila, R.C. Baliban, C.A. Floudas.  Nationwide Energy Supply Chain Analysis for Hybrid Feedstock Processes with Significant CO₂ Emissions Reduction. AIChE J., submitted.